EP0078579B1 - Méthode d'utilisation d'un faisceau d'électrons - Google Patents

Méthode d'utilisation d'un faisceau d'électrons Download PDF

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Publication number
EP0078579B1
EP0078579B1 EP82201358A EP82201358A EP0078579B1 EP 0078579 B1 EP0078579 B1 EP 0078579B1 EP 82201358 A EP82201358 A EP 82201358A EP 82201358 A EP82201358 A EP 82201358A EP 0078579 B1 EP0078579 B1 EP 0078579B1
Authority
EP
European Patent Office
Prior art keywords
marker
markers
beam spot
area
predetermined position
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82201358A
Other languages
German (de)
English (en)
Other versions
EP0078579A2 (fr
EP0078579A3 (en
Inventor
Hewson Nicholas Graham King
James Patrick Beasley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Electronics UK Ltd
Koninklijke Philips NV
Original Assignee
Philips Electronic and Associated Industries Ltd
Philips Electronics UK Ltd
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Electronic and Associated Industries Ltd, Philips Electronics UK Ltd, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Electronic and Associated Industries Ltd
Publication of EP0078579A2 publication Critical patent/EP0078579A2/fr
Publication of EP0078579A3 publication Critical patent/EP0078579A3/en
Application granted granted Critical
Publication of EP0078579B1 publication Critical patent/EP0078579B1/fr
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H01J37/304—Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
    • H01J37/3045—Object or beam position registration

Definitions

  • This invention relates to a method of using an electron beam to effect sequentially a process at two adjacent surface areas of a target, reference markers being provided at predetermined positions between the areas, which method, after effecting the process at one area includes the steps of shaping the electron beam so as to produce at the target surface a beam spot having substantially the same size and shape as each marker, directing the beam spot towards the area of each reference marker, detecting the resulting back-scattered electrons from each marker to provide a signal representative of any deviation between the actual and predetermined positions of each marker, and responding to said signal by compensating for any such deviation when effecting the process at the second area.
  • a so-called electron beam pattern generator can be used to direct an electron beam towards a target in the form of a semiconductor substrate coated with an electron sensitive resist.
  • a predetermined pattern can be drawn in the resist.
  • the exposed parts (or, in the case of a negative resist, the unexposed parts) of the resist are then removed selectively using an appropriate chemical.
  • the remaining parts of the resist form on the surface of the semiconductor substrate a masking layer which can be used subsequently in the processing of the semiconductor wafer.
  • the area (sometimes called the deflection field) which can be scanned by the electron beam is somewhat restricted because of the occurrence of electron optical aberrations which increase markedly as the electron beam deviates more and more from the optical axis. This presents a problem when large areas of resist are to be exposed.
  • the beam can be used to draw one pattern at a first area of the substrates before moving the substrate to introduce a new area of the substrate to the electron beam.
  • the same (or a different) pattern can be drawn at this new area without the need for the beam to have an unduly large deflection field.
  • a conventional pattern generator produces an electron beam which, at the target, is circular and has a Gaussian intensity distribution. As the beam has a typical diameter of 0.2 micrometre it can fairly be described as a point beam.
  • the point beam is made to draw the outline of each rectangle and then to fill it in by scanning the rectangle before proceeding to the next rectangle.
  • the substrate is moved so that the same pattern can be drawn at the next area as described above.
  • the semiconductor substrate Before the semiconductor substrate is exposed to the electron beam it is usual to perform an initial, relatively coarse alignment of the substrate. Nevertheless, it is still possible for alignment errors to be introduced during device manufacture as a result of instabilities in either the electron beam pattern generator or in the semiconductor substrate. For example, the semiconductor substrate can become distorted as a result of the various treatments to which it is subjected. To compensate for any such errors it is usual to employ a reference marker system on the substrate surface.
  • the electron beam can be directed towards the predetermined position of a marker to derive a signal representative of the deviation between the actual position and the predetermined position of that marker. This signal can then be used either to correct the substrate movement or to add a correction factor to the electron optical system so that the next time the electron beam draws the pattern it does so at the correct location.
  • the reference marker may be a depression in the semiconductor substrate, for example a square of 20 micrometresx20 micrometers.
  • a marker may be located at the four corners of each such area.
  • the beam is directed, in turn, towards the four reference markers at the corners of that area.
  • the beam is scanned, for example 8 times across each edge of the marker, the scan direction being transverse to the edge in question. By observing the back-scattered electrons the deviation between the actual position and the predetermined position of the marker can be determined. To minimize errors, similar information is gathered from each of the four markers at the corners of a particular area before the pattern is drawn at that area.
  • variable spot-shaped electron beam system is ideally suited to drawing patterns in a resist coating on a semiconductor substrate, particularly when the pattern can be decomposed into basic rectangular elements. In this case the time taken to draw a pattern at a given area can be deceased considerably. This has the important consequence that pattern generators producing variable spot-shaped electron beams can have an increased throughput as compared with their point beam counterparts.
  • a method as referred to in the opening paragraph characterised in that an array of similar reference markers is provided between the areas, each marker being at a predetermined position, and in that the method comprises the steps of directing the beam spdt towards the area of each reference marker in turn, and integrating the signals from each marker in the array to give an average value for said deviation.
  • the beam current can be considerably higher than that of a point beam. This has the advantage that the number of back-scattered electrons can be significantly higher so that the detection of position errors can be carried out more quickly.
  • the reference marker may have a different topology to the surrounding area of the target and/or it may be constituted by an area of material having a different back-scattering coefficient to the material of the target.
  • the reference marker when the target is a silicon substrate coated with an electron-sensitive resist the reference marker may be an island of silicon oxide or of a metal such as tantalum formed directly on the substrate surface.
  • the reference marker may be a depression at the surface of the target formed, for example, by etching with an appropriate chemical.
  • the reference marker may have any geometric shape, but matching the shape of the electron beam to the reference marker is particularly straightforward when the reference marker is square.
  • the provision of a plurality of similar reference markers between the two areas of the target is particularly advantageous not only because the effects due to the presence of a poorly-defined reference marker can then be minimized, but also because the signal-to-noise ratio of the detected signal can be increased for improved accuracy and greater speed.
  • the method may be characterised in that the beam spot is directed to the predetermined position of each marker in the array in turn, and in that the back-scattered electrons are detected using two pairs of detectors arranged such that the detectors of at least one pair provide different signals when the predetermined position of a marker deviates from the actual position, the differential signal from a detector pair representing the extent of the deviation in the direction parallel to the line joining the two detectors of that pair.
  • the method may be characterised in that the beam spot is directed towards a succession of positions on the target surface such that the beam spot coincides with the predetermined position of only a chosen one of the reference markers and is progressively misaligned with each other marker spaced further from the chosen marker, in that a single detector is used to determine the position errors of the reference markers, and in that the signals from all the markers are utilised to give said average value.
  • this method allows accurate determination of position errors using only a single detector.
  • the array of reference markers mentioned above may be an irregular array, but the detection of alignment errors is particularly straightforward when the markers are arranged in a regular manner, for example in a single row or in a plurality of rows and columns.
  • a semiconductor wafer 1 is located on a movable table 2 of a variable spot-shaped electron beam pattern generator.
  • the wafer 1 is coated on the major surface directed away from table 2 with a layer 3 of electron sensitive resist.
  • the wafer 1, which is generally circular, may have a diameter of approximately 100 mm (4 inches) and it is divided into areas 3 millimetres square where a process is to be effected sequentially using the electron beam 4.
  • an integrated circuit may be formed in conventional manner.
  • Figure 2 shows several such areas 5 on a greatly distorted scale.
  • the spacing between adjacent areas 5 may be for example 100 micrometres. None of the circuit elements of the integrated circuits is formed in the space between adjacent areas, because this represents the so-called scribe lane where the semiconductor wafer 1 will later be severed to divide it into individual integrated circuits.
  • the markers may, in fact, be squares of 3 micrometers spaced apart by 6 micrometres. Therefore, for a scribe lane 100 micrometres wide and 3 millimetres long the array will comprise 10 columns of 300 markers.
  • These reference markers 7 may be formed by chemically etching the silicon wafer in known manner. Depending on the way in which the etching is performed the depressions may have vertical sides as shown in Figure 3a, sloping sides and a horizontal bottom as shown in Figure 3b, or four sloping sides which meet at a point, as shown in Figure 3c. Typically these depressions may be 1 micrometre deep.
  • variable spot-shaped beam is used to selectively expose one of the areas 5 of the wafer 1 which is coated with resist. This process is carried out to define in the resist a pattern so that selective removal of the unexposed (or, as the case may be, the exposed) parts of the resist 3 leave a masking layer for use in subsequent processing of the semiconductor wafer in the manufacture of integrated circuits.
  • the table 2 is moved to introduce an adjacent area 5b into the deflection field of the electron beam.
  • the table is adapted to move in directions parallel and orthogonal to the scribe lanes in which the reference markers 7 are provided.
  • the electron beam has a square shape with sides of 3 micrometres.
  • This beam having the same size and shape as the markers 7 is directed towards the predetermined position of each of the markers 7 in turn.
  • the beam is stepped, relative to the wafer 1, from marker to marker by an amount equivalent to the spacing of the markers.
  • the back-scattered electrons are detected using four detectors 9, two in the X-direction and two in the Y-direction.
  • Each detector 9 of a pair is equally spaced from the marker so that a differential signal is set up across the detectors of a pair if the predetermined position of a marker deviates from its actual position.
  • the detectors 9 are connected to a differential amplifer D.
  • Figure 1 shows two detectors only, the other two detectors being provided in the direction orthogonal to the plane of the paper.
  • the differential signal obtained from the differential amplifier D is representative of both the extent and the direction of any deviation between the predetermined position and the actual position of the reference marker 7 in question.
  • the output signal 0 can be used in compensating for any such deviation when effecting the electron beam exposure process at the next area 5b. Consequently, the next time the electron beam draws a pattern it does so at the correct location. This may be achieved by adding a correction factor to either the table movement or to the electron optical system.
  • variable spot-shaped beam position errors can be detected very quickly, so much so that the table can be moving between subsequent processing treatments while the alignment error detection is taking place simultaneously.
  • the throughput of semiconductor wafers in the pattern generator can be significantly increased.
  • the same two dimensional array 6 of similar reference markers 7 can be provided between adjacent areas 6 of a semiconductor wafer 1 as described above with reference to Figure 1.
  • the electron beam is directed towards the area of each reference marker in turn, but the beam is stepped, relative to the wafer 1, from the area of one marker to the area of an adjacent marker by an amount which is either more or less but not the same as the spacing of adjacent reference markers.
  • the beam may be stepped by 6.05 micrometres.
  • the beam has the same size and shape as the individual reference markers 7, that is to say it is 3 micrometres square, but in contrast with the previous method the beam is directed towards the predetermined position of the reference marker at the centre of the array only.
  • the beam will be coincident with one reference marker only, viz. the marker at the centre of the array, and it will be misaligned with all the other markers.
  • Figure 4 shows three plots of the signals obtained under different circumstances. Plot A represents no deviation between the predetermined position and the actual position of the central reference marker.
  • Plot B represents the situation where the beam has been aligned with a reference marker in the negative X-direction
  • Plot C represents the situation where the beam has been aligned with a reference marker in the positive X-direction.
  • Similar information for the Y-direction can of course be obtained by plotting the signal intensity for the reference markers in the Y-direction. This information indicates the extent of any correction which may be needed to ensure that the electron beam is correctly aligned when effecting the element process at subsequent areas.
  • the correction factor may be applied to the movement of the table on which the semiconductor wafer is mounted or to be electron optical system.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Beam Exposure (AREA)
  • ing And Chemical Polishing (AREA)

Claims (5)

1. Procédé d'utilisation d'un faisceau d'électrons en vue d'effectuer séquentiellement un processus dans deux zones superficielles adjacentes d'une cible, des marqueurs de référence étant prévus en des endroits prédéterminés entre les zones, ce procédé comprenant, après la réalisation du processus dans une zone, les opérations consistant à conformer le faisceau d'électrons de manière à produire, sur sa surface de la cible, un spot en substance de même dimension et de même forme que chaque marqueur, à diriger le spot du faisceau vers la zone de chaque marqueur de référence, à détecter les électrons rétrodiffusés résultants de chaque marqueur pour fournir un signal représentatif d'une quelconque déviation entre la position réelle et la position prédéterminée de chaque marqueur, et à réagir au dit signal en compensant cette déviation éventuelle au moment où le processus est effectué dans la seconde zone, caractérisé en ce qu'un ensemble de marqueurs de référence semblables est prévu entre les zones, chaque marqueur se trouvant dans une position prédéterminée, et en ce que le procédé comprend les opérations consistant à diriger le spot du faisceau successivement vers la zone de chaque marqueur de référence, et à intégrer les signaux de chaque marqueur de l'ensemble pour donner une valeur moyenne pour la déviation.
2. Procédé suivant la revendication 1, caractérisé en ce que le spot du faisceau est dirigé vers la position prédéterminée de chaque marqueur de la série successivement, et en ce que les électrons rétrodiffusés sont détectés au moyen de deux paires de détecteurs disposées de telle façon que les détecteurs d'au moins une paire fournissent des signaux différents lorsque la position prédéterminée d'un marqueur dévie de la position réelle, le signal différentiel d'une paire de détecteurs représentant l'importance de la déviation dans la direction parallèle à la ligne reliant les deux détecteurs de cette paire.
3. Procédé suivant la revendication 1, caractérisé en ce que le spot de faisceau est dirigé vers une telle succession de positions sur la surface de la cible que le spot du faisceau ne coïncide qu'avec la position prédéterminée d'un seul des marqueurs de référence qui a été choisi et soit progressivement désaligné par rapport à chaque autre marqueur davantage espacé du marqueur choisi, en ce qu'un seul détecteur est utilisé pour déterminer les erreurs de position des marqueurs de référence et en ce que les signaux de tous les marqueurs sont utilisés pour donner la valeur moyenne.
4. Procédé suivant la revendication 2 ou 3, carctérisé en ce que les marqueurs de référence de l'ensemble sont disposés d'une manière régulière, les centres des marqueurs étant espacés d'une distance constante (d).
5. Procédé suivant la revendication 4 découlant de la revendication 3, caractérisé en ce que le spot du faisceau est déplacé pas à pas successivement sur la surface de la cible d'une distance différente de (d), la position de départ et la longueur du pas de déplacement étant choisies telles que le spot du faisceau coïncide en substance avec la position prédéterminée du marqueur de référence choisi.
EP82201358A 1981-11-02 1982-10-29 Méthode d'utilisation d'un faisceau d'électrons Expired EP0078579B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8132927 1981-11-02
GB08132927A GB2109538A (en) 1981-11-02 1981-11-02 Electron beam alignment

Publications (3)

Publication Number Publication Date
EP0078579A2 EP0078579A2 (fr) 1983-05-11
EP0078579A3 EP0078579A3 (en) 1985-08-07
EP0078579B1 true EP0078579B1 (fr) 1989-01-04

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP82201358A Expired EP0078579B1 (fr) 1981-11-02 1982-10-29 Méthode d'utilisation d'un faisceau d'électrons

Country Status (5)

Country Link
US (1) US4503334A (fr)
EP (1) EP0078579B1 (fr)
JP (1) JPS5884976A (fr)
DE (1) DE3279331D1 (fr)
GB (1) GB2109538A (fr)

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2159939A (en) * 1984-03-02 1985-12-11 Hewlett Packard Co Detector apparatus
GB2157069A (en) * 1984-04-02 1985-10-16 Philips Electronic Associated Step and repeat electron image projector
US4713169A (en) * 1985-01-08 1987-12-15 Phillips Petroleum Company Fluid feed method
JPS6229135A (ja) * 1985-07-29 1987-02-07 Advantest Corp 荷電粒子ビ−ム露光方法及びこの方法を用いた荷電粒子ビ−ム露光装置
US4936930A (en) * 1988-01-06 1990-06-26 Siliconix Incorporated Method for improved alignment for semiconductor devices with buried layers
JPH02231708A (ja) * 1989-03-06 1990-09-13 Fujitsu Ltd 半導体装置の位置合わせマーク検出方法及び装置
US5523576A (en) * 1993-03-15 1996-06-04 Kabushiki Kaisha Toshiba Charged beam drawing apparatus
KR0139702B1 (ko) * 1993-06-22 1998-07-15 사토 후미오 반도체장치 및 그 제조방법과 얼라인먼트방법
JP3034428B2 (ja) * 1993-06-22 2000-04-17 株式会社東芝 半導体装置及びその製造方法並びにアライメント方法
US6184524B1 (en) 1996-08-07 2001-02-06 Gatan, Inc. Automated set up of an energy filtering transmission electron microscope
US5798524A (en) * 1996-08-07 1998-08-25 Gatan, Inc. Automated adjustment of an energy filtering transmission electron microscope
US5936252A (en) * 1996-10-01 1999-08-10 International Business Machines Corporation Charged particle beam performance measurement system and method thereof
US6576529B1 (en) 1999-12-07 2003-06-10 Agere Systems Inc. Method of forming an alignment feature in or on a multilayered semiconductor structure
GB2372150B (en) * 1999-12-07 2003-09-10 Lucent Technologies Inc A method of forming an alignment feature in or on a multi-layered semiconductor structure
US20020170887A1 (en) * 2001-03-01 2002-11-21 Konica Corporation Optical element producing method, base material drawing method and base material drawing apparatus

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3840749A (en) * 1973-06-19 1974-10-08 Westinghouse Electric Corp Method and apparatus for electron beam alignment with a semiconductor member
JPS5283177A (en) * 1975-12-31 1977-07-11 Fujitsu Ltd Electron beam exposure device
JPS5512784A (en) * 1978-07-14 1980-01-29 Chiyou Lsi Gijutsu Kenkyu Kumiai Location mark for electron beam exposure

Also Published As

Publication number Publication date
EP0078579A2 (fr) 1983-05-11
EP0078579A3 (en) 1985-08-07
GB2109538A (en) 1983-06-02
DE3279331D1 (en) 1989-02-09
US4503334A (en) 1985-03-05
JPS5884976A (ja) 1983-05-21

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